In a universal mobile telecommunication system (UMTS), when a user equipment (UE) in a cell dedicated channel (CELL_DCH) state moves and signal strength of a cell that currently serves the UE suddenly decreases, or the UE enters a neighboring cell at a very fast moving speed, a radio network controller (RNC) cannot switch the UE to a new cell in time while a current cell cannot serve the UE. In this case, if after sending downlink signaling or downlink data for a plurality of times, the RNC receives no acknowledgment returned by the UE, or the RNC receives a radio link failure indication message sent by a base station (NodeB), the RNC may release a radio resource control (RRC) connection of the UE, resulting in a failure of a communications service being performed by the UE, for example, call drop. Therefore, reliability of the communications service decreases. Other communications systems also have similar problems.